Evaluation of Irrigation Practices and Nutrient Management to Close the Gap in Furrow Irrigated Rice

Investigators: Anna Smyly and Drew Gholson

Date: 2022

Project Summary

Introduction

Rice (Oryza sativa L.), in Mississippi, is typically grown using a continuous flood production system that requires large inputs of water throughout the growing season. On average, rice uses approximately 3.0-acre feet per year of water, which based on average acreage of rice production equates to approximately 600,000- acre feet per year being pumped in Mississippi. Irrigation water in the Mississippi Delta is extensively drawn from the Mississippi River Valley alluvial aquifer (MRVAA). The MRVAA is beginning to deplete at a rate of 300,000-acre feet per year and irrigation water is becoming scarce. Determining a more efficient irrigation approach is vital to the sustainability of the aquifer for agricultural needs. Research in Mississippi has shown furrow-irrigated rice (FIR) to produce rice with less water, but there is limited information on how to efficiently irrigate and fertilize FIR. The objective of this study was to evaluate the effect of 4 different irrigation frequencies on soil moisture, water depth levels, water use efficiency (WUE), and rice grain yield of FIR.

Materials and Methods

Research was conducted at the Delta Research and Extension Center in Stoneville, MS on Sharkey clay soil in 2021, 2022, and will continue in 2023. The arrangement of the experiment design was randomized complete block, including 4 irrigation frequencies on a calendar-based schedule of irrigating every day, every 3, 5, and 7 days. Rice variety CLL16 was planted into freshly pulled beds spaced at 96 cm and a seeding rate of 73 lbs./ ac. Treatment plots were 8 rows wide with a levee constructed on either side of the rice plot to keep irrigation frequency treatments separated. Soil moisture, water depth levels, and water usage were recorded before and after each irrigation occurrence from the top, middle, and bottom one-thirds of each treatment plot using WaterMark® Soil Moisture Sensors®, Pani-Pipes®, Precision King AgSense Sensors®, and flowmeters. Rice grain yield was taken from the middle 2 rows of each treatment plot and analyzed using statistical analysis software (SAS).

Results and Discussion

Average rice grain yield (bu ac-1) was measured for each treatment plot across the whole plot, as well as the three different zones within the plots. Table 1 shows average yields for 2021.The study observed in 2021 treatment plots irrigated every day, numerically, had the highest average yield (152 bu ac-1) compared to the other 3 irrigation timings. Average rice grain yields for irrigating every 3 days (144 bu ac-1) and every 5 days (143 bu ac-1) weren’t significantly different from each other. Irrigating every 7 days produced the lowest yield (140 bu ac-1) of the 3 irrigation treatments. Yield is numerically different, but not significantly different between the different zones in the treatment plots. Table 2 shows average yields for 2022. In 2022, there were no significant differences between average yields of each irrigation frequency treatment. Table 3 shows the 2021 and 2022 combined average yields for the top, middle, and bottom zones of each irrigation frequency treatment. The bottom zone resulted in a significantly greater average yield compared to the top zone for irrigation frequency treatment.

Conclusion

The 2021 study suggests irrigating FIR every day will produce a higher rice grain yield compared to irrigating every 3, 5, or 7 days. Treatment plots irrigated every day closely mimic a continuous flood production system, which could explain why watering FIR every day produced a higher rice grain yield. The study also suggests a farmer won’t see a significant difference in yield when deciding whether to irrigate every 3 or 5 days. However, the 2022 study contradicts these findings in 2021 by finding no significant differences between the average yields of the 4 irrigation treatments. Lodging and consistent irrigation water delivery down the furrows in some irrigation treatment plots was an issue in 2022, which could have led to smaller yield differences and more similar yields. Constructing a well built-up seed bed with straight furrows is important for irrigation water delivery in FIR. Water usage, soil moisture, and water depth levels are still being analyzed. The study will be repeated again in 2023.

• Topic:
• Irrigation Scheduling
• Irrigation